I second the lampeye killis. I have never been a fan of typical schooling fish but I have about 10 of these guys and they are awesome! Whenever people see my tank they ask about the blue eye fish
I am also a huge fan of dario dario. A lot of personality in a small fish. They are fearless!
Something no one else has mentioned yet are shell dwellers. Now they aren't really community fish but they are facinating. Neolamprologus multifasciatus is a great beginner shell dweller. They form colonies where older fry will actually help take care of new fry. I have some Neolamprologus Occelatus "gold". Another fish with a lot of attitude. They will actually attack the siphon when vacuuming the tank. They have no idea they are tiny!
I know it's not a fish but dwarf cray fish are also pretty interesting. I love seeing them wave their tiny claws at me when I look in the tank. They are small enough to be safe with plants and small fish.

I am also a huge fan of dario dario. A lot of personality in a small fish. They are fearless!
Something no one else has mentioned yet are shell dwellers. Now they aren't really community fish but they are facinating. Neolamprologus multifasciatus is a great beginner shell dweller. They form colonies where older fry will actually help take care of new fry. I have some Neolamprologus Occelatus "gold". Another fish with a lot of attitude. They will actually attack the siphon when vacuuming the tank. They have no idea they are tiny!
I know it's not a fish but dwarf cray fish are also pretty interesting. I love seeing them wave their tiny claws at me when I look in the tank. They are small enough to be safe with plants and small fish.